Reciprocal computing mechanism



Feb. 11, 1958 E. K. GRIP El'AL 2,822,981

RECIPROCAL. COMPUTING MECHANISM Filed Feb. 27, 1956 2 Sheets-Sheet 1 IN VEN TOR. Er/A Konrad Gr) film BY-4Q" Gusfav Hell ATTOHIVEK;

Feb. 11, 1958 E. K. GRIP ETAL RECIPROCAL COMPUTING MECHANISM 2 Sheets-Sheet 2 Filed Feb. 27, 1956 FIG.3

United States Patent RECIPROCAL COMPUTING MECHANISM Erik Konrad Grip and Lars Gustav Hellstrom, Atvidaberg,

Sweden, assignors to Aktiebolaget Atvidaberg-Facit, Atvidaberg, Sweden, a joint-stock company of Sweden This invention relates to calculating machines and is particularly concerned with mechanisms for computing reciprocals in calculating machines which are adapted to perform division automatically.

When computing a reciprocal in calculating machines of known design a one is entered as a dividend at the extreme left of the accumulator, and is subsequently divided by the number, the reciprocal of which is desired.

The invention has for its object to provide mechanism which will facilitate the computation of a reciprocal in that a one need not be entered as a dividend.

According to the invention the overdraft control impulse is rendered ineffective during the first revolution when the product accumulator has been cleared, a divisor has been entered into the actuator of the machine (e. g. calculating rotor) and the starting key has been actuated, the division being performed in such a manner as if a one had been entered into a calculating wheel beyond the highest denomination in the product accumulator.

Mechanism embodying the invention will now be described as being applied to a calculating machine known per se, e. g. of the kind of described in U. S. patent specification No. 2,398,286.

In calculating machines of the kind referred to the division cutting-off impulse is initiated by the overall tens transfer, so that a stepwise displacement of the actuator (calculating rotor) takes place as soon as the number in the accumulator changes its sign.

In the appended drawings:

Fig. 1 is a detail of a division control mechanism generally similar to that of Fig. 3 of U. S. patent specification No. 2,398,286 referred to above, the mechanism being shown in elevation,

Fig. 2 is a view similar to Fig. 1 but showing certain parts in a different position, and

Fig. 3 is an end view of the mechanism of Figs. 1 and 2.

The mechanism embodying the invention comprises a rocking arm 1 pivotally supported at 2 on a division arm 3. A division pawl member 4 is pivotally mounted at 5 on rocking arm 1. The division pawl member 4 is urged by a spring 6 into engagement with a tens transfer hook 7 which is operated by the highest denominational order of the accumulator during division in a manner known per se (of U. S. patent specification No. 2,398,286, wherein the transfer hook is designated 100). If the division pawl member 4 is engaged (Figs. 2 and 3) it will transmit the movement of hook 7 to a bail member 8 which transfers movement in a manner known per se to the drive transmitting mechanism of the machine so that the movement of the actuator (calculating rotor) is arrested.

The rocking arm 1 may assume two different positions, and is coupled for that purpose to an arm 9 which is pivoted on a pivot 10. The operation of arm 9 is controlled by two cam members 11 and 13, respectively, the former fixed to a shaft 12 and the latter to another shaft 14. Arm 9 is locked in either of its two positions by a ice latch member 15 which is urged toward a stud member 17 by a tension spring 16.

When shaft 14 rotates, arms 9 and 1 are moved to the position illustrated in Fig. 1 wherein pawl member 4 cannot actuate bail member 8 even if the hook 7 should assume its operated position. When shaft 12 rotates however, the arm 9 is moved into the position illustrated in Fig. 2 in which rocking arm 1 and pawl member 4 are held in such a position that the movement of the transfer hook 7 is transmitted to bail member 8.

Shaft 14 is arranged to perform a revolution each time the accumulator is cleared. Thus, after clearing, pawl member 4 will assume such a position (Figure 1) that bail member 8 is not actuated.

The operation of shaft 12, on the contrary, is entirely controlled by the rotation of the calculating rotor in such a way that it performs a revolution in the positive or negative sense for each revolution of the rotor. The cam curve 11 has a cam member 11a disposed in such a manner that it does not engage the arm 9 until the end of the revolution when rotating in the negative sense. For this reason pawl member 4 is disengaged during the whole of the first revolution in the negative sense and is only engaged at the end of said revolution.

When a division operation is started, the initial movement is always a revolution in the negative sense of the actuator. Since the accumulator will have been cleared immediately before the initiation of the division, a revolution in the negative sense will occur before the arm 9 is actuated by the cam curve 11 and in its turn actuates arm 1 which moves pawl member 4 in below bail member 8. Thus the division operation is not stopped despite the fact that the transfer hook 7 is operated, and the actuator (calculating rotor) continues to operate until the transfer hook is again operated. In this manner the same result is obtained as if an assumed one had been entered in an additional number wheel beyond the highest denomination of the accumulator, and thus the reciprocal of the divisor is computed without any dividend being visible. It is, of course, necessary in order to obtain this result, that the accumulator be cleared prior to the initiation of the division operation.

The invention is not limited to the illustrated embodiment, but can be applied with the same effect to other types of calculating machines, the different parts having, of course, to be adapted to the design of the respective machines.

What we claim is:

1. In a calculating machine adapted to perform division by repeated subtraction and having a clearable accumulator, an accumulator actuator and means operated by the highest order tens transfer mechanism of the accumulator to step the actuator denominationally with respect to the accumulator upon occurrence of an overdraft; means for calculating the reciprocal of a divisor entered into the actuator comprising, normally interposed means for transmitting movement of the tens transfer mechanism to the actuator stepping means, means operated by the accumulator clearing means for removing said interposed means from interposed position and means operated by said actuator at the termination of the following entry cycle of the actuator to restore said movement transmitting means to interposed position.

2. A reciprocal calculating mechanism as claimed in claim 1, wherein said normally interposed means is a member mounted for movement into and out of position between a bail of the actuator stepping mechanism and the tens transfer mechanism.

3. A reciprocal calculating machine as claimed in claim 2, wherein said means operated by said accumulator clearing means comprises a cam driven by the clearing means,

and cooperating with said movable member to move it from position betweenthe bail and the tens transfer mechanism.

4. A reciprocal calculating mechanism as claimed in cla'ihi 2' Whi'eiii' Said mea'fiS OPi'QteKi by $515 tiififofis" 7' a cam driven by the actuator and. cboperating With Said movable member to move it between the bail and the References Cited in the file of this patent UNITED STATES PATENTS Friden Aug. 16, 1932 Carlstrom Apr. 9, 1946 Avery Aug. 17, 1948 

